Stringed musical instrument



I Sept. 17, .w ESPIE I STRINGED MUSICAL INSTRUMENT Filed march 8, 1927 ATTORNE Y.

Patented Sept. 17, 1929 JOHN W. GILLESPIE, OF CINCINNATI, OHIO S'IBINGEDMUSICAL INSTRUMENT Application filed March 8, 1927. Serial No. 173,744.

My invention relates to stringed musical instruments of the type ofbanjo. ukulele or the like, in which music is produced by playing onstrings which cause the vibration of a tympanum or diaphragm which ismounted in a tubular supporting member.

It is the object of my invention to construct the support for thetympanum, so that a maximum of strength will be achieved, and so thatthe additional strengthening means which I provide will greatly clarifythe tone of the notes and cause more mellow, bell-like tones to beemitted from the instrument than has been possible in such instrumentsprior to my invention.

Referring to the drawings in which I have shown a preferred structure ina banjo which embodies my invention Figure 1 is a plan View of a banjohead.

Figure 2 is a section of the head taken along the lines 22 in Figure 1.

Figure 3 is a detail section taken along the lines 33 in Figure 1.

Figure 4 is a diagram of the probable audio principle involved in mynovel structure.

The banjo illustrated in Figures 1-3 is composed of a tympanum 1 mountedon a wooden tubular casing member 2, which I will refer to as the head.7 The tympanum which is ordi- 36 narily made from some strong animalfibrous membrane is bound at its edges in adjustable annular memberswhich will permit the tympanum to be tightened and released inaccordance with the conditions to which the instrument is subjected. Forsupporting the edges of the tympanum I have shown, as is in accordancewith standard banjo manufacturing practice. a hoop 3 and a stretcherband or wire 4. The edges of the tympanum 0 are passed under the band 4,then up on the bearing downwardly on the top surface of the hoop. Theposts are mounted in lugs 6 which are interspaced about the outerperiphery of the tubular support and secured to the support with screwssuch as are indicated at 7. The posts have threaded ends which extendthrough the lugs and nuts 8 are mounted on the threaded ends. Bytightening up the nuts one after another, it will be obvious that thetympanum or diaphragm may be tightened, and by slacking off on the nutsthe tympanum will be loosened.

The playing strings for the banjo are inclicated at 9. The usual methodof securing the strings is in a plate 10, which is secured to thetubular support as indicated in Figure 2 with pin posts 11 which extendthrough an outwardly flanged portion 12 of the plate. The pin posts havethreaded ends Which pass through lugs 13 which are attached to thetubular support in a similar manner as are the lugs 6, by screws 14. Theplate 10 has grooves therein and in each one of the grooves a string isengaged usually by knotting the end of the string. The strings pass upover the face of the tympanum over a bridge 15 mounted on the tympanumin the usual manner.

The description of the construction, so far given. forms no part of myinvention, being explained merely so as to enable one skilled in the artto copy the exact structure which I have found most satisfactory in abanjo instrument.

My invention consists primarily in the structure of the wooden tubularsupport 2 for the tympanum which is that part of the instrument whichcontributes to the quality of the music thereof. I have shown at thebase of the member 2 an internally flanged wooden rib 16 which it willbe apparent is of considerable importance in supporting the tubularmember against a collapsing strain which is often present in suchinstruments as a banjo. Banjos are very often provided with cross ribswhich extend across the opening in the tubular support, and although Imay equip a banjo made in accordance with my invention with such a rib,its presence or lack does not materially affect the practical resultthat the wooden reinforcing rib 16, which is preferably beveled fromlines parallel to the sides of said head toward lines projected alongradial lines extending from the axis of the head, materially increasesthe anticollapsing strength of the tubular sound box.

In Figure 4 I have illustrated diagrammatically my theory of the effectof the rib on the tone of the instrument. I have shown a tympanum whichis indicated at a. The tubular support is indicated at Z). The effect ofsound waves on one side of the tympanum without the rib 0 is indicatedby the dotted lines at the bottom of the figure. WVhile a vibration ofthe tympanum causes impulses on one side of the tympanum, counterimpulses are caused by the inward movement of the tympanum on the otherside thereof. The cycle is alternately reversed and repeated on each ofthe sides of the tympanum in accordance with the rate of vibration ofthe sound wave. If the tubular support is not provided with anything tointerfere with the free travel around the corner edge of the support,the effect is for the plus and minus waves, as they may be called, toneutralize each other, as is indicated by the dotted lines at the lowerend of the figure. With the flanged reinforcing rib, however, indicatedat the upper side of the figure, the tree path of tone vibrations fromone side of the tympanum to the other is restricted and a Louder andmore vibrant sound is heard, due to the sound waves being turnedinwardly toward the axis of the head. It will be observed that the soundwaves within the tubular support are turned back, each on the other, andthey reverberate within the head. A resonance which gives the tonalquality of a bell results. I have indicated the path of travel of thesound vibrations in an instrument constructed in accordance with myinvention by the wavy solid lines shown in Figure 4.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent, is

1. In a stringed musical instrument, a tympanum and a wooden tubularresonant support for said tympanum, said support being open at its ends,and a Wooden reinforcing peripheral rib extending about one end toreinforce the tubular support, said rib acting as a battle to increasethe resonance of said support, said rib extending inwardly adjacent theouter periphery of said tubular support, and having a concaveinner Wall.

2. In a stringed musical instrument, a tympanum and a wooden tubularresonant support for said tympanum, said support being open at its ends,and a wooden reinforcing peripheral rib extending about one end toreinforce the tubular support, said rib acting as a bafile to increasethe resonance of said support, said rib extending inwardly adjacent theouter periphery of said tubular support, and portions of said ribconcavely beveled to deflect sound Waves inwardly toward the axis ofsaid support.

3. In a banjo, an open ended resonant support for the diaphragm thereof,and a wooden rib formed adjacent the open end of said support, said ribbeing beveled from lines parallel with the Walls of said support andcurving concavely toward the axis of said support whereby sound waveswithin said support will tend to be deflected back into said support,whereby the tonal quality of said banjo will be improved.

JOHN WM. GILLESPIE.

